[Exim] problem with relaying and dns-blacklist

hi out there,

i was just handling spam by dns-blacklists.. thats working fine, i use a
database lookup
but i noticed that some mails got no host entry......or something like
that.. my output says:

2002-06-08 20:17:10 17FKC4-0007kC-00 ** jrico@??? R=dnslookup
T=remote_smtp: SMTP error from remote
mailer after RCPT TO:<jrico@???>: host smtp-in.compaq.net
[207.46.181.125]: 550 5.1.1
jrico@???... User unknown

yes, i see this user was not at the destination domain and was rejected
y the remote server, but how can i
figure out from where this mail comes??????? and stop relaying this kind
mails ..... what about the ** entrys? i
dont understand it anymore... to much readmes... please can you help?

volker